Drop down in a table view.

Table view is created using AET.

It has 5 colums.

1) product category (f4 help).

2)comp1 (which is ddlb).

Based on the f4 value selected ,the ddlb values has to be populated.

like if product category is "categor1 " selected ,the comp1 values should be "comp1 ,comp2 ,comp3,comp4" ..(taken from custom table).

for the 2nd row ,if "category 2" slected ,the comp1 values should be "comp4,comp5" ..(taken from custom table).

How can i achive this ?

Thanks.